共查询到20条相似文献,搜索用时 15 毫秒
1.
J. K. Haywood I. Robertson K. Boddy 《Journal of Radioanalytical and Nuclear Chemistry》1979,48(1-2):117-124
A 14 MeV neutron generator system with a new sealed tube (Philips 18604) was evaluated for total body in vivo neutron activation
analysis (TBIVNAA). The neutron output, angular distribution, rise time, reproducibility of short irradiations and leakage
of tritium were investigated. The 18604 tube meets all the requirements of TBIVNAA within its normal operating specification. 相似文献
2.
《Radiation Physics and Chemistry》2009,78(5):311-317
At any neutron production facility, the energy spectrum at any meaningful distance from the target will be modified. For the case of a facility used to provide reference irradiations of electronics and other devices at various target-to-device distances it is important to have knowledge of these spectral modifications. In addition, it is desirable to have the ability to generate near real-time measurement capability. Advances in neutron metrology have made it possible to determine neutron energy spectra in real time to high levels of accuracy. This paper outlines a series of experimental measurements and theoretical calculations designed to quantify the scattering effects for a 14 MeV neutron generator facility, and makes appropriate recommendations for near real-time measurements of these fields. 相似文献
3.
I. M. Valente M. J. Minski P. J. Peterson 《Journal of Radioanalytical and Nuclear Chemistry》1982,71(1-2):115-127
Detection limits are presented for the platinum metals in vegetation for different neutron activation analysis conditions,
namely, short irradiation, cyclic and long irradiations both thermally and epithermally. These detection limits for instrumental
neutron activation analysis are compared with those using preconcentration technique—dry ashing and fire assay and post irradiation
separation of the platinum metals using Srafion NMRR in exchange resin. The results are evaluated for plant material and it
is concluded that dry ashing followed by cyclic, epithermal irradiation for rhodium and palladium and long, thermal irradiations
for osmium, platinum, iridium and ruthenium enable these elements to be detected in plants at background levels. 相似文献
4.
《International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry》1986,27(1):35-39
ESR combined with the spin-trapping method was applied to a study of the effects of both γ- and neutron irradiations to n-eicosane. Two kinds of crosslinks were detected; one was the crosslinks at ends of chains and the other was the crosslinks in central parts of chains. Another radical, which was a secondary carbon radical and presumably a precursor for the crosslinks, was also detected. Either by the temperature change or by the radiation dose variation the conformation changes were found for the secondary carbon radical, which was a good probe for the difference in the crosslinks. Some difference was also found in the effect of the γ- and neutron irradiations to n-eicosane. 相似文献
5.
By combining instrumental and radiochemical neutron activation analysis, up to 47 elements including major, minor, and trace elements, have been determined in lake sediment samples. Instrumental neutron activation involving both short and long irradiations is used to determine 40 elements including most of the environmentally important ones. A radiochemical separation procedure allows the determination of 7 noble metals. The accuracy and precision of the method are 5–10%. 相似文献
6.
S. S. Krishnan M. T. Bayley A. J. W. Hitchman S. C. Lin K. G. McNeill J. E. Harrison 《Journal of Radioanalytical and Nuclear Chemistry》1987,114(1):173-180
This work describes an in vivo neutron activation analysis facility for small samples, such as rats or human hand, using two 100 g252Cf neutron sources. The irradiation area is a cylindrical space, of 12 cm diameter and about 15 cm length, with fairly uniform neutron flux distribution. Experimental data on the reproducibility, effects of volume and other conditions for in vivo measurements are given. Comparative atomic absorption data on calcium measurements on rats are reported. The facility is now used for animal experiments as well as human hand irradiations in clinical investigations involving calcium metabolism and bone diseases. 相似文献
7.
A method for simultaneous neutron activation determination of Al, Mg and Si using two irradiations in a nuclear reactor—the first one with epithermal and the second one with pile neutrons is proposed. The applicability of the method is demonstrated by the analysis of standard reference materials—rocks, glass, as well as of archaeological finds from medieval glass and sgraffito ceramics. 相似文献
8.
P. Schramel W. Schmolke B. -J. Klose 《Journal of Radioanalytical and Nuclear Chemistry》1979,53(1-2):89-95
The described method is suitable for the determination of about 20 trace-elements by neutron activation analysis and radiochemical
group separation with one standard (flux-monitor) instead of the simultaneous irradiation of the elements investigated. The
activity of the flux-monitor delivers the correction-factor, under the same irradiation conditions (neutron spectrum), between
the irradiation of a complete standard-set and the different irradiations of unknown samples. The FRN (Research Reactor Neuherberg)
is not working continuously so that it is necessary to add different irradiation times of some hours to our routine irradiation
time of 24 hours. The correction factors for these complicated working conditions in neutron activation analysis are mathematically
described and discussed.
相似文献
9.
Instrumental neutron activation analysis (INAA) has been applied for the simultaneous determination of up to 33 elements including major, minor and trace elements in the environmental reference materials soil and coal fly ash from China. The procedure involves both short and long irradiations followed by the measurement of the gamma spectra with a Ge(Li) detector. The analytical results are presented and discussed. 相似文献
10.
Xilei Lin D. Alber R. Henkelmann 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(3):531-538
This work is about k
0-INAA using unstable neutron flux for sample irradiation. Due to slow transport, each irradiation in the channel DBVK consists of three phases: stable irradiation at the final position, and two additional irradiations during travelling by exposure to an increasing neutron flux in the delivery course and to a decreasing neutron flux in the fetch course. In this work, the neutron flux distribution along this channel was calibrated and the neutron flux variation with irradiation time was calculated, making it possible to evaluate activity growth during a complete irradiation period. The feasibility of the k
0-method was checked by analyses of four SRM-materials and three multi-element standards at three DBVK-positions. An accuracy of better than ±10% was found for nearly all determined elements in each determination. 相似文献
11.
P. Jagam J. -X. Wang J. J. Simpson 《Journal of Radioanalytical and Nuclear Chemistry》1993,171(2):277-286
Improvements in the detection limits of thorium and uranium in acrylics by neutron activation analysis are described. The average of results from 10 g samples was found to be higher than the results from 450 g samples taken from the same acrylic sheet. Using eighteen large (450 g) samples from a single sheet of acrylic gave an average value of 3.2±0.3 pg/g thorium and 1.1±0.7 pg/g uranium. Interpretation of the results is discussed. Epithermal neutron activation with Cd shielded irradiations did not improve the detection sensitivity for thorium. 相似文献
12.
Neutron activation analysis is applied to the determination of Ga, Th and U in Bauxite and coal ash; thermal and epithermal irradiations are used. The other analytical methods are also quantitatively surveyed for gallium. The results indicate that epithermal neutron activation is prefered for those trace elements because the former method is more simple and quick. 相似文献
13.
S. Ahmad M. S. Chaudhary I. H. Qureshi 《Journal of Radioanalytical and Nuclear Chemistry》1981,67(1):119-125
An instrumental neutron activation analysis technique has been developed for the simultaneous determination of up to 30 elements
including major, minor and trace elements in Obsidian Rock (a proposed NBS-SRM-278). INAA method involves both short and long
irradiations followed by gamma-ray activity measurement with a Ge(Li) detector. The accuracy of the procedure has been checked
by analyzing IAEA Reference Materials. 相似文献
14.
S. J. Reddy E. Mauerhofer N. Porte J. Damodar H. O. Denschlag 《Journal of Radioanalytical and Nuclear Chemistry》1998,238(1-2):83-90
Levels of As, Ba, Br, Ca, Ce, Cl, Cr, Cs, Eu, Fe, Hg, I, K, La, Mg, Mn, Na, Ni, Rb, Sb, Sc, Sm, Sr, Th, Zn, and U have been
determined in ten leaves widely used in ayurvedic medicine by instrumental neutron activation analysis (INAA). The neutron
irradiations were performed with a 100 kW Triga nuclear reactor and the induced activity was counted with a gamma-ray spectrometer.
Based on elemental levels obtained the utility of these leaves in medicine are discussed. 相似文献
15.
Nasir Khalid Mohammad Wasim Nadeem A. Lodhi Mohammad Arif 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(1):153-159
Certified alloys of Ni–Cu based, Fe based and Cu–Sn based were analysed by semi-absolute, standardless k 0-instrumental neutron activation analysis (k 0-INAA) and flame atomic absorption spectrophotometry (FAAS) aiming at evaluating their comparative performances. In k 0-INAA measurements, the irradiations were performed at miniaturized neutron source reactor having thermal neutron flux of about 1 × 1012 cm?2 s?1. The experimentally optimized parameters for INAA suggested a maximum of three irradiations for the quantification of 21 elements within 5 days. The same experiments also produced quantitative results of 13 elements not reported in the certificates of the reference materials. AAS was, however, unable to determine any of those elements. Accuracy of the two techniques was assessed by comparing their average root mean squared errors. The data analysis concluded that k 0-INAA had better sensitivity and accuracy than FAAS. 相似文献
16.
I. Obrusník B. Stárková J. Blažek 《Journal of Radioanalytical and Nuclear Chemistry》1976,31(2):495-502
Instrumental neutron activation analysis (INAA) has been utilized for the analysis of 19 different fly ashes, 1 sample of
coal and 3 samples of industrial emissions. Both short and long irradiations in a nuclear reactor have been used. The irradiated
samples have been measured by means of a computer-based Ge(Li) gamma-ray spectrometer. The concentrations of 27 elements have
been determined in the samples. 相似文献
17.
M. D. Glascock W. Z. Than W. D. Ehmann 《Journal of Radioanalytical and Nuclear Chemistry》1985,92(2):379-390
A boron nitride irradiation vessel designed for use with a pneumatic tube transfer system has been used to analyze short-lived radionuclides by NAA. Bare and Cd-shielded irradiations on Co, Zr and Au were made to characterize the neutron fluxes in the irradiation position. Bare and BN-shielded irradiations were performed to determine epithermal advantage factors for 16 short-lived reactions and interference factors for a total of 11 (n, p) and (n, ) reactions induced by reactor fast neutrons. To illustrate application of these data, several biological and geological reference materials were analyzed. 相似文献
18.
L. De Norre J. Op De Beeck J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1983,78(1):137-148
A method has been developed for routine determination of cadmium in zinc ores by thermal neutron absorption analysis, based
on the attenuation of a thermal neutron flux passing through a neutron absorbing material. The thermal neutron flux is related
to the52V-activity induced in a vanadium detector, surrounded by pellets pressed from a mixture of powdered material with graphite.
Besides cadmium, also the major constitutents zinc, iron and sulfur contribute significantly to the total attenuation of the
thermal neutron flux. Calibration lines for these elements are worked out. All irradiations are carried out for 200 s in the
partially thermalized neutron flux of a 5 Ci227Ac—Be isotope neutron source. After a decay of 30 s, the52V-activity of the vanadium detector is measured for 400 s with a NaI(T1) scintillation detector. The analysis sequence, including
the computation of the results from the counting data, is automated by means of a LSI—11 microprocessor with 12K×16 bit memory.
Zinc ores, containing 0.02 to 1.45% cadmium, have been analyzed with a precision ranging from 12.6% to 0.54% relative. As
a test for the reliability of the method, two NBS standard reference materials were analyzed in the same way as the zinc ore
samples. 相似文献
19.
Lin Xilei F. De Corte L. Moens A. Simonits J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1984,83(2):333-343
A scheme for instrumental neutron activation analysis of ancient and medieval glasses is proposed. The combination of three irradiations (short time, pile and epithermal) enables the determination of 34 elements. The accuracy of the method is evaluated by analyzing two glass standard reference materials. Results from the analysis of three glasses from different times are presented. 相似文献
20.
M. V. Frontasyeva V. M. Nazarov E. Steinnes 《Journal of Radioanalytical and Nuclear Chemistry》1994,181(2):363-371
Instrumental activation analysis (INAA) based on irradiations in a nuclear reactor with particularly high relative fluxes of resonance and fast neutrons has been shown to open new possibilities for multi-element surveys of mosses used as monitors of atmospheric deposition. Comparison is made with data obtained by inductively coupled plasma-mass spectrometry (ICP-MS) and conventional INAA. Data for 15 elements not previously investigated in routine moss studies are presented, e.g., Zr, Sn, Hf, Ta, W, Au, Th, and the rare earth elements Ce, Nd, Eu, Gd, Tb, Tm, Yb, Lu. Other elements particularly well determined by this approach are Sc, Co, As, Ag, Sb, Cs, La, Sm, Th, and the non-metallic trace elements Se, Br, and I. Advantages and drawbacks with the high fast neutron component are discussed. 相似文献